Aliphatic Acids: Influence on Sulfate Mobility in a Forested Cecil Soil

Dissolved organic substances derived from forest litter are believed to influence the retention and movement of SO 2− 4 in forest soils. A column study was conducted in which 35 SO 4 was surface applied to a soil and leached with either low‐molecular‐weight aliphatic acids (AA) or a forest‐litter extract. Oxalic, malonic, and succinic acids were used in the concentration range 8.0 × 10 −3 to 1.0 × 10 −5 mol L −1 . Movement of 35 SO 4 was determined with column depth, as was the 35 SO 4 activity in the collected leachates. Labeled SO 4 soil movement was found to increase with increasing AA concentration. Leachate 35 SO 4 activity was observed to increase in the order malonic > succinic > oxalic for acid treatments > 1.0 × 10 −4 mol L −1 . The 1.0 × 10 −5 mol L −1 acid treatments did not result in 35 SO 4 break‐through in the soil columns. Reduced exchangeable 35 SO 4 for organic acid ≥ 1.0 × 10 −3 mol L −1 suggests that at high concentrations, aliphatic acids may activate sulfate retention sites in soil, while at lower concentrations these acids may accelerate the movement of 35 SO 4 in forest soils due to selective organic‐acid adsorption by soil components.